The present invention relates to manufacturing plants and methods for manufacturing cement clinker.
A method and a plant of the aforementioned kind are known e.g. from WO 2005/100247. In this known plant a portion of the calcined raw meal is extracted using a small additional cyclone which is positioned parallel to the separation cyclone of the calciner. According to the patent application the quantity of material which is extracted by means of the additional cyclone can be adjusted using a gate which is located in the discharge duct for the gases from the aforementioned additional cyclone. Typically, the temperature of the gases which are diverted via the discharge duct from the additional cyclone will be about 900° C., and in actual practice it has proved to be very difficult to provide a gate which is capable of operating reliably at such a temperature. Also, the gases may contain some amount of alkali which may be quite sticky due to the high temperature, and therefore having a tendency to clog at and around the gate, entailing risk of the gate getting stuck.